The present invention is directed to a pyrolytic system for the conversion of organic feedstreams, such as waste feedstreams, into usable, valuable end products. Specifically, the present invention is directed to a self-sustaining pyrolytic apparatus and process for converting waste materials into a beneficial, activated carbon and a combustible gas products.
Organic materials in the form of fossil fuels such as coal and crude oil or renewable resources such as forests and food materials have previously been manufactured directly and indirectly into products and by-products eventually treated as waste. Such waste has been and continues to be in dry, moist and wet forms emanating from industrial, mining, agricultural and municipal sources such as liquid and solid municipal wastes. All various man-made waste materials continue to be emitted worldwide to land, air and waterways causing recognized pollutants such as classified "greenhouse" gases, dioxins and toxic compounds of metals. All of these are subject to environmental scrutiny and regulatory emissions control. Such deleterious emissions are the result of mistreatment as waste when the same materials can be useful as feedstock for the systems to be disclosed and claimed herein as the invention.
While partial pyrolysis (incomplete combustion) techniques have been practiced in the past, there are no known commercial systems of ongoing pure pyrolysis operations. Separation is a process step whereby after the mixture of substances and the chemical compounds comprising the composition of a feedstock are transformed into different chemical compositions and phases being intermediate products and are divided into separate containment. Because such separation resists forces and the conversion of heat to work is limited by the temperature at which conversion occurs, it is a costly step with partial pyrolysis in terms of the energy to make separation occur. Other techniques such as pressure and cryogenics are also not preferred for separation of mixed components within the process stream. Pressure swing adsorption, molecular sieves, activated alumina and zeolites may be used for separation but these are also limited and not preferred for many applications.
Conventional plants use the combustion of materials to generate steam from water in a boiler. The process by which such steam drives a steam turbine to generate electrical power and is thereafter returned to water is known as the Rankine cycle. Such plants are complex in design and require substantial investments in large equipment and real estate. Furthermore such systems emit polluting exhausts and create large quantities of ash which must be landfilled. As an alternative, a variety of pyrolytic processes, some of which may be employed in the disposal of waste feedstocks, have been proposed.
U.S. Pat. No. 4,145,274, is directed to a continuous process for recovering product gas and carbon char from an organic feedstream which includes a flash pyrolysis zone as well as means for preparing the initial carbonaceous material for pyrolysis, product recovery means and a gas cleanup operation. However, the process requires that the carbonaceous material is comminuted to a particle size of less than about 1000 microns in diameter and transported to the pyrolysis zone in a carrier gas which has a solids content of no more than about 10% by volume. A particulate source of heat may be derived from the oxidation product of recovered solids.
U.S. Pat. No. 4,153,514 is directed to a pyrolysis process for solid wastes which is similar to that of the '274 patent, discussed above, but which requires that waste solids comminuted to a particle size of no more than one inch are mixed with hot particulate carbon char in the carrier gas prior to entering the pyrolysis zone.
U.S. Pat. No. 4,162,959 is directed a pyrolysis process wherein simultaneous pyrolysis and hydrogenation reactions occur within a pyrolysis zone. Comminuted carbonaceous material contained within a carrier gas is fed into a pyrolysis zone along with hydrogen recovered from a conversion zone. Hydrogen and other gases are formed in the conversion zone wherein hot char particles obtained from the pyrolysis zone are reacted with steam. Steam is also injected into the pyrolysis zone to react with the hot particulate char contained there to generate additional hydrogen gas to further hydrogenate the volatized hydrocarbons resulting from the pyrolysis of the carbonaceous material.
U.S. Pat. No. 4,166,786, is directed to a process which is similar in many aspects to that of the '959 patent discussed above. However, rather than introducing steam into the pyrolysis zone as disclosed in the '959 patent, a vapor mixture which includes volatilized hydrocarbons and unreacted hydrogen gas which is recovered from the pyrolysis zone is separated from the carbon containing residue and hydrogenated in the presence of a catalyst in a vapor hydrogenation zone.
U.S. Pat. No. 4,260,473 is directed to a pyrolysis process for solid organic wastes which requires separation of solid product of pyrolysis from pyrolysis vapor which contains entrained particulate matter, condensing at least a portion of the pyrolysis vapor, centrifuging the resultant liquid and separating it into different fractions.
U.S. Pat. No. 4,356,077 is directed to a pyrolysis process similar to that disclosed in the '274 patent, discussed above. However, rather than in an inert carrier gas, the comminuted carbonaceous material is transported into the pyrolysis zone in a "beneficially reactive gas." Such is defined as a gas which is substantially free of free oxygen and which contains gaseous constituents which inhibit the reactivity of the char product and the carbon containing particulate solid source of heat. Following pyrolysis the pyrolytic vapors are quenched and separated by vacuum flashing prior to further separation and enrichmert steps.
U.S. Pat. No. 4,357,228 is similar to the '077 patent, discussed above, in that it is directed primarily to post-pyrolysis processing of pyrolysis vapors quenching and vacuum flashing steps.
U.S. Pat. No. 4,375,402 is directed to a pyrolysis process similar to that disclosed in the '274 patent, discussed above. However, following pyrolysis particulate solids are separated from the gas product which is, in turn, is immediately contacted with a quench fluid which contains at least one capping agent which stabilizes the newly formed volatilized hydrocarbon free radicals contained in the gaseous mixture and condenses most of the larger hydrocarbons.
U.S. Pat. No. 3,853,498 is directed to a process for the gasification of waste which includes an endothermic pyrolysis zone which is a bed of fluidized, inert particulate solids and an exothermic combustion zone which is also a bed of inert particulate solids with the heat for pyrolysis being transferred from the combustion zone by circulating the inert particulate solids between the two zones.
U.S. Pat. No. 4,002,438 is directed to a pyrolytic apparatus having a pyrolysis reaction chamber and a combustion chamber. Recycled product carrier gas and a dense, hard, abrasion resistant material, such as sand, are circulated through the apparatus to transfer heat from the combustion chamber to the pyrolysis chamber.
U.S. Pat. No. 4,578,175 is directed to a combined process for coal pyrolysis and char gasification. Finely divided coal is mixed with a hydrogen-containing recycle gas stream and is introduced into the lower region of a vertical pyrolysis zone along with finely divided heated char. The resulting mixture passes upwardly through the pyrolysis zone at a temperature between 500 and 950.degree. C. and a pressure between about 3 and about 33 atmospheres. Gas, liquid and solid product streams are removed from an upper region of the pyrolysis zone. Thereafter, product solids are introduced into the lower region of a vertically elongated fluidized bed gasification zone for treatment with an oxygen containing gas.
U.S. Pat. No. 5,245,762 is directed to an apparatus and method for drying sludge wherein batches of sludge are received by a loading device and then transported to a series of conveyors containing driven augers with the conveyors forming a closed loop circulating path for the sludge. Means for heating and circulating air around the conveyors without contacting the sludge as well as means for heating and circulating air through the sludge are provided. A sensor determines moisture content and activates a means for discharging the sludge when the moisture content of the sludge reaches a predetermined level.
Thus, as may be seen from a review of the patients discussed above, all known prior art pyrolytic systems or devices are complicated in design and operation, inefficient, and generally produce unwanted or unnecessary products and byproducts of incomplete combustion including contaminated wastewater, oils, tars and sludge. The need remains to have a system to provide improved and optimum conditions for time, temperature and turbulence of materials in the absence of air and pressure to efficiently and safely produce products having desired chemical compositions and properties. A further need is to have the process consistent with the system to control chemical reactions of the products and further process those products to form additional and more desirable products which can be easily separated and used within and outside the process.